docs: def disable_ipv6():
      """
      Disable ufw IPv6 support in /etc/default/ufw
      """
      exit_code = subprocess.call(['sed', '-i', 's/IPV6=.*/IPV6=no/g',
                                   '/etc/default/ufw'])
      if exit_code == 0:
          hookenv.log('IPv6 support in ufw disabled', level='INFO')
      else:
          hookenv.log("Couldn't disable IPv6 support in ufw", level="ERROR")
          raise UFWError("Couldn't disable IPv6 support in ufw")